Information about Conjoined Twins

There is an extremely rare form of identical twins that occurs perhaps in one out of every 75,000 to 100,000 births or 1 in 200 deliveries of identical twins, that of conjoined twins.

Conjoined twins originate from a single fertilized egg so they are always identical and same-sex twins. The developing embryo starts to split into identical twins within the first two weeks after conception but then stops before completion, leaving a partially separated egg which continues to mature into a conjoined fetus.

The birth of two connected babies can be extremely traumatic and approximately 40-60% of these births are delivered stillborn with 35% surviving just one day. The overall survival rate of conjoined twins is somewhere between 5-25% and historical records over the past 500 years detail about 600 surviving sets of conjoined twins with more than 70% of those surviving pairs resulting in female twins.

While there are dozens of types of conjoined twins, doctors generally divide the types into the more common variations described in the below chart. All of these types can be more broadly categorized as displaying either equal and symmetrical forms or unequal and possible asymmetrical forms.

Perhaps the most famous pair of conjoined twins were Eng and Chang Bunker, who were born in Siam (now Thailand) on May 10, 1811 and died within hours of each other on January 17, 1874 at age 62. The Bunker Twins fathered 21 children between them and were successful businessman and ranchers in Wilkes County, North Carolina. Attached by a five-inch connecting ligament near their breastbones, Eng and Chang married sisters Sallie and Adelaide Yates, respectively, and lived fairly private lives when they weren't touring the world to earn incomes. After their deaths it was determined they could have been successfully separated, a medical option that was never offered to Eng and Chang during their lives.

Although Eng and Chang's fame helped coin the phrase 'Siamese Twins', they were not the first pair of conjoined twins recorded in medical annals as there were probably about 100 such pairs known by the time of their 1811 births, a fact which helped the King of Siam reverse an early death sentence on the brothers. In fact, conjoined twins were recorded as early as 945 in Armenia and the first pair of successfully separated twins took place in 1689 by German physician G. König.

While there aren't any documented cases of conjoined triplets, there have been triplet births that featured conjoined twins, most recently Nida and Hira Jamal of Pakistan. Although the two Craniopagus girls were successfully separated, tragically Nira's heart wasn't strong enough after the separation and she died shortly after the operation.

Today, most pairs of conjoined twins are successfully identified during prenatal examinations. Some types of conjoined twins are much easier to separate while other rare forms lead to complicated and costly procedures that can lead to difficult ethical and moral decisions of separation surgery, especially if the twins share internal organs (the case of Baby Jodie and Baby Mary in England in 2000 being a perfect example). The European case (their parents are from the Maltese island of Gozo) in which one baby was allowed to die during surgery brings back memories of conjoined sisters Angela and Amy Lakeberg of Indiana, who also shared just one heart when born. They were separated August 20, 1993 in a ceremony in which Amy was allowed to die. Tragically, Angela died less than a year later. According to the book 'Entwined Lives', there have been approximately 200 attempted surgical separations of conjoined twins, with 90% of these occurring after 1950. Three-quarters of the procedures since 1950 have resulted in one or both of the twins surviving.

Several hospitals across the world specialize in these often difficult surgeries. The Children's Hospital of Philadelphia has performed more than a dozen successful separation surgeries since its first operation in 1957 (most recently performing one on 7-month-old twin girls on March 1, 2001), while physicians such as Dr. Rich Hampton of the Pediatric Surgical Associates in the Twin Cities of Minneapolis and St. Paul, successful separated Keri and Kaci Archer in October, 1991. The Children's Hospital of Boston has operated on nine sets of conjoined twins (as of the mid 1990's, current numbers not available). Raffles Hospital in Singapore took on the extremely difficult operation of separating 29-year-old Iranian conjoined twins Ladan and Laleh Bijani in July, 2003. While they were able to successfully separate the skulls of this craniopagus set of twins, tragically they were not able to successfully separate the blood stems from their two separate brains and both ladies died on the operating table on July 8th, 2003.

There are organizations which can help parents of conjoined twins address some of the issues they will face during their pregnancies or while raising their children. Conjoined Twins International, based in Prescott, Arizona, was founded in 1987 by a grandfather of conjoined twins. The organization gives advice and support to a little more than half of the families of conjoined twins currently living in the United States.

Chronological History of Conjoined Twins
Types of Conjoined Twins